1. Field of the Invention
The present invention relates to a power transmission device of an automobile, and in particular relates to a power takeoff unit for distributing torque from first axles to second axles in a four-wheel drive vehicle for example.
2. Description of the Related Art
In a front-wheel drive vehicle for example, an engine installed on the front of a vehicle body generates torque and a differential receives and distributes the torque to left and right front wheels. In a case of a four-wheel drive vehicle, for the purpose of distributing part of torque to rear wheels, a power takeoff unit (PTU) is in general used in combination with a transmission including a differential. A casing of the PTU and a transmission case are mutually securely combined in order to prevent eccentricity of these rotation shafts and then used.
Oil is required to circulate throughout the interior of the transmission case for the purpose of lubrication. Separate from this circulation, another oil is required to circulate within the PTU. To prevent mutual mixing, an oil seal is in general disposed at the boundary between the transmission case and the PTU. This oil seal is required to intervene there with sufficient repulsive force in order to prevent oil leakage through the periphery of the rotation shaft. Thus, in a case where the oil seal is disposed within the PTU at the side opposed to the casing, the oil seal is, after assembly of the PTU, pressed from its end into the PTU around the periphery of the rotation shaft with considerably great pressure.
Japanese Patent Applications Laid-open No. 2004-314796, 2009-115309, U.S. Pat. No. 4,739,678 A, and Japanese Patent Application Laid-open No. 5-155265 disclose related arts.